Structure and Reactivity of the N-Acetyl-Cysteine Radical Cation and Anion: Does Radical Migration Occur?

TitleStructure and Reactivity of the N-Acetyl-Cysteine Radical Cation and Anion: Does Radical Migration Occur?
Publication TypeJournal Article
Year of Publication2011
AuthorsS. Osburn, G. Berden, J. Oomens, R.AJ O'Hair, V. Ryzhov
JournalJournal of the American Society for Mass Spectrometry
Volume22
Number10
Pagination1794-1803
Date PublishedOct
Type of ArticleArticle
ISBN Number1044-0305
Accession NumberWOS:000295088400013
KeywordsAMINO-ACIDS, CRYSTAL-STRUCTURE, DFT calculations, DIRECTED DISSOCIATION, GAS-PHASE, INFRARED-SPECTROSCOPY, Ion-molecule, IRMPD SPECTROSCOPY, N-acetyl-cysteine, PEPTIDE RADICALS, radical ions, Radical rearrangement, reactions, RESONANCE MASS-SPECTROMETRY, RIBONUCLEOTIDE REDUCTASE, THIYL RADICALS
Abstract

The structure and reactivity of the N-acetyl-cysteine radical cation and anion were studied using ion-molecule reactions, infrared multi-photon dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. The radical cation was generated by first nitrosylating the thiol of N-acetyl-cysteine followed by the homolytic cleavage of the S-NO bond in the gas phase. IRMPD spectroscopy coupled with DFT calculations revealed that for the radical cation the radical migrates from its initial position on the sulfur atom to the alpha-carbon position, which is 2.5 kJ mol(-1) lower in energy. The radical migration was confirmed by time-resolved ion-molecule reactions. These results are in contrast with our previous study on cysteine methyl ester radical cation (Osburn et al., Chem. Eur. J. 2011 , 17, 873-879) and the study by Sinha et al. for cysteine radical cation (Phys. Chem. Chem. Phys. 2010 , 12, 9794-9800) where the radical was found to stay on the sulfur atom as formed. A similar approach allowed us to form a hydrogen-deficient radical anion of N-acetyl-cysteine, (M - 2H) (aEuro cent aEuro") . IRMPD studies and ion-molecule reactions performed on the radical anion showed that the radical remains on the sulfur, which is the initial and more stable (by 63.6 kJ mol(-1)) position, and does not rearrange.

URL<Go to ISI>://WOS:000295088400013
Division

GUTHz

Department

Molecular Dynamics

PID

af72fe84bdefb1df9b83e70449ef2ea4

Alternate TitleJ. Am. Soc. Mass Spectrom.

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